Let-off mechanism for looms



Jan. 27, 1931.

J. NORTHROP LET-OFF MECHANISM FOR LOOMS Filed Oct. 10. 19 28 2 Sheets-Sheet 1 Jan. 27, 1931. .1. NORTHROP LET-OFF MECHANISM FOR LOOMS Filed Oct. 10, 1928 2 Sheets-Sheet 2 WWI/e56 F Lida Patented Jan; 27, 1931 UNITED. [STATE PA-TE T pflFricg-j j '1 aonns nonrrrnonor HOPEDALE, trassncnusn'r'rs, Assmms T STANDARD Looms,

INC., 013 MILFORD, MASSACHUSETTS, A 'CORP ORATIQN OF SOUTH CAROLINA LET-err MEcnANIsMroR LOOMS a. Application' filed October ,0, 1928.1 Serial no. 311,524.

The present invention relates to let-off mechanisms for looms. v e

-' Dne objectof the present invention is to provide aletoff mechanism by whicha substantlally UlllfOIHl tension on the warp is maintained at all times." v A further object of the invention is to provide a let-ofi mechanism in which the amount of let-ofi is accurately controlled in accordance with the diameter of the warp beam. A still further object of the invention is to provide means whereby the warp beam may be conveniently rotated by hand from the front of the loom without interference by the let-off mechanism. Y 1 To these ends, the present invention consists of the let-01f mechanism hereinafter described and particularly defined in the claims.

In the accompanying drawings, Fig.1 is aside view of so much" of a loom as is necessary to an understanding of the present inventiomwith the improved let-off mechanism applied thereto'; Fig. 2 is a view similar to Fig.1 showing the let-ofi and associated parts but' on an enlarged scale; Fig. 3is a rear view of the apparatus shown in Fig. 2; Fig.

4 is a section-on line 44 of Fig. 2;'.Fig.- 5 is a detail view similar'to Fig 4 but showing the pawl in raised position; Fig. 6 is a sectional detail view of the hand release-mecha i nism'; Fig. 7 is a view similar to 6' with the-mechanism in'released position; Fig. 8 is an end view ofthe hand operated release; andFig, 9 is a section on'line9'9 of Fig. 6.

'The illustrated embodiment of the invention comprises a loom frame 10 to the rear of which is suitably attached aframe 12 for supporting-the warp beam-and the let-off at the front ofthe loom in-aheadj24 attached thereto which is at a convenientheight for access by the operator for the purpose of per mitting manual rotation of the'warp beam, as will presently beexplained in detail,

mechanism; The warp beam is shownat 14,"

Fixed on the shaft 22 is a ratchet 2 6 7 adapted to be intermittently rotated by a pawl 28 pivoted onapawl arm 30 and urged toward: engagementwith the ratchet byfla compression spring 32. A" link "84 connects thepawl arm with the end of a'bell crank lever 36 which is secured toa rock shaft 38' journaled 'in'the frame 12. The upwardly extending arm 40 of the bell cr'ank'consists' of a I positioning 'arm which determines the amount of movement oflthe pawl in accordancefwith the tension on'the' warp, as will hereinafter be described. -"Secured to therockshaft 88 and depending therefrom is a lever 42 having at its end'a' pin- .44' received in a slot 46, in a reciprocating head 48. The head 48-is connected by a rod 50 with the lay sword 52 and is continuously reciprocated by the movements of the latter.

Itwill be seen that as the actuator'head 48' is recip'rocated by the m'otion ofthe lay sword, .itsg-engagementwith the lever 42 will cause the pawl to" move back and forth over the ratchet. A forward movementof the swordfpr'oduces a forward or let-off movement of the pawl and'a rearward beat of the sword permits the pawl to retract by gravityoverthe ratchet teeth, because of the lost motion connection afforded by the slot,

46. The amount: .OfllQt-Off will depend upon the position'ofsthe pin 44,'that' is to say, it will depend upon the point at which therear end of the slotted member picks up the pin, V

because-while the lay' sword undergoes a uniform movementjthe pin 44 will undergo a 5 variable movement and thereby cause a {variable let-oif of the warp. 1

It will be seen "that since the pawl I ratchet are disposed' -in a substantially vertical plane, restoration of the pawl by gravity is permitted, thereby avoiding the necessity foraspring. I

The positioning'of the pin 44 with relation to-the-head 48, by which the amount of throw of the let-off pawl is determined, is accomplished in' the following'ma'nner; In the illustrated embodiment of the invention, 2 the whip roll'54 over which the vwarps pass from the warp beam is mounted in brackets eygn'eat eachjside at the; loom, which 7 brackets are pivoted at 58 on a stationary part ofthe frame. The whip roll is urged toward its rearwardmost position by. the usual heavy springs 60. Depending from the rear end of the bracket 56 is a projection 62 slotted at 64 to afford an adjustable connection for an arm 66 which; is bolted thereto. Pivoted to the end of the arm 66 is an adiustable link 68 which receives the threaded end of a long spring positioning rod 7 0. r The rod 70 is downwardly inclined and n'ear its lower end it passes freely through a spring control bushing 72. A long compression spring 74 encircles the rod, 7 0 and bears at opposite ends against the bushing 7 2 and a washer 76 near the upper end of therod. The bushing 72 has a hub 77 secured to arock shaft 7 8 which extends across the loom, the compression of the spring being variedaccording tothe angular position of the rockshaft. Inasmuch as the arm 66 is rigidly secured to the projection 62by' the bolt'and slot connection, the spring 74 resists pivotal .movement of the whip roll bracket 56gas-the warp puts tension on the whip roll The arm 66 carries a pin 79 whichis received in a slot 80 in the-end ofga pawl positioning lever 82 pivoted at 84 on the frame 12. The lower end of the lever-lies in the path of the upper arm 40 of the 'bel-lcrank. It will be seen that if the war-p tension increases, the whip roll willbe depressed and the lever 82 will be swung in" a counterclockwise direction so that the bottom end of the lever will be moved toward the right, as viewed in Fig. 2. This will permit the upper arm of the bell crank lever 40 to move toward theright and hence the pin H will be permitted to follow farther toward the rear of the loom upon a retracting movement of the pawl, so that on the next forward beat of the lay, the head 48 will pick up the pin 4A relatively sooner in the time of travel and hence'impart an ;increased"motion to the pawla The mechanism thus far described assures the pro'perlet-off in accordance withthe tension that maybe placedon the warp. Thus,

if the warp has for-any reason been let off too 'slowly, the n creased' tension occasioned 7 thereby will resultin' a wider swing of the pawl and a restoration of proper let-off conditions, Incidental variations in warp tension suiiic-ient to require changes in the let-off arise from severalfa'ctors, such as variations in the rate of take-up of the finished cloth, resistance to passage of the threads through the reed and harnesses, and the like.- Aside I from these, however, there is a tendency toward a progressivelyincreasing tension due to the diminution-of the diameter" of-the warp beam as the warp is used; -As the diam- ,eter decreases, it isnecessary that the/beam turn faster to, compensate for thediminished let-off for; each revolution; A mechanism as described above will satisfactorily maintainthe proper feed, but it will be noted that since the feed is itself controlled by the warp tensiomthe increasing rate of rotation of the beam as its diameter decreases is accompanied byan increasing tension on the warp threads. It is desirable, however, especially in silk weaving, to maintain a substantially uniform warp tension at all times, and to this end the present invention afiords means 7 for varying the-sensitivity: of the warp tension lct-oif control in accordance with the diameter of the warp beam. In the'preferred form of the invention, thisresult is attained by varying the compression of the spring 7 l, whereby its resistance tothemovement of the whip roll is varied. To'this end, the bushing 72 against which the lower end of the spring bears is variedin position in accordancewith the amount of warp on the beam. A warp follower 90 having at its upper end a ro1l'92 to engage the warp beam is also secured to the rock shaft 78 at 94:. The compression of the 'spring74 tends to maintain the warpfollower roll 92 in engagement with the w'arpfi "i is the-warp decreases in size, the follower swings in a counter-clockwise direction, as viewed in Fig. 2, thereby slightly relieving the compression on thespring 74 andpermitting the whip roll bracket 56 to.

oscillate on its pivot. 58 with greater facility.

Thus, when the warp beam is relatively small, the whiproll acting under the tension of'the the warp beam may be rotated by;.han'd in. either direction without interference bythe I let-off mechanism. :The mechanism by which this result is accomplished; will now; be -defscribed; The head 24 which is mounted on the end of the worm shaft 22- at the front of the loom comprises afldisk which is secured to;the shaft22by a pinhlQOw The disk has a facing 102 of-leather or other friction material adapted tobear under normal operating conditions against the face of a clutchdog-104k. Thedog is slidingly mounted on the shaft 22 and is maintainedagainst rotation by a bracket 106 attached to the 100m frame. The dog is recessed at 108 to embrace the squared'portion of=thebracket 106 whereby the dog may be free to slide on the bracket but is held against rotation. The.

oppositesides of-the bracketiare provided with projections 110- which serve, as pivotal ntings-fer aztippigiglev rllli shown I in Fig. 9, the lever is made in the form ofa hollow rectan le which surrounds the do 104, the lower end thereof abutting a shoulder 115 on the dog. A rod 114 connects the up per edge of the rectangular lever 112 with a bell crank lever. 116 which terminates at 1ts rear end in a pawl lifterllS. 5 A coiled compressionspring 120bearing against the up er end of the bell crank 116 normally holds the .parts in the position shown 1n F g. 1,

the pawl lifter being out of engagementwith the pawl 28. Under normalrunning conditions, the frictionalengagement of the clutch dog 104 with the friction facing 102, afiords snificient resistance to the rotation of the I shaft 22 to prevent overrunning of the ratchet the position shown-in Fig. 7, the dog 104is pushed rearwardly, thereby rocking the lever 112 on itsfpivots and exerting a pull on the 'rod 114. This movement of the pawl crank lever swin s the pawl lifter 118 into the position shown in Fig. 5, so that the lifter engages a pin122 extending from the side of the pawland thereby lifts the pawl out of engagement with the ratchet.' The same movement of the cam disengages the dog from the frictionfacing and thereby relieves the friction so that the shaft 22 can be easily turned by means of the handle 124 in either 7 direction. The engagement. of the cam with the face of the dog 104 is not suflicient to 7 into engagement with the ratchet.

resist easy manual rotation of the shaft and moreover, it maintains the dog in the position shown in Fig. 7 until such time as it is desired to restore the loom to normal operating conditions. Upon pfishing the handle 124 to its original position, as shown in Fig. 6, the lifter 118 is moved to inoperative position by the spring 120and the pawl is permitted to move It will be seen that the hand control is disposed entirely at the front of the loom, where it is most conveniently accessible to the operator. Having thus described the invention, what is claimed is:

1, A loom having, in combination, a warp beam, let-off mechani m including a pawl and ratchet, a shaft on which the ratchet is mounted extending to and terminating at the front of the loom, a pawl lifter, a head on the front of the shaft, a handle for rotating'the head, and means controlled by the handle for operating the pawl lifter.

- 2..A loom having,in combination, a warp beam, alet-offmechanism including a shaft l extending from-the warp beam to the'front of the loom, gearing between the shaft and the warp beanna pawl and ratchet forrotatg l. x '7 ing the shaft, a friction device by which rotation of the shaft is resisted in normal oper-' ation, a pawl lifter, and manually operated means for simultaneously operating the pawl lifter and releasing the friction device to permit the shaft to be turned by hand. f

3. A loom having, in combination, a warp beam, a let-off mechanism including a pawl and ratchet, a shaft on which the ratchet 1s mounted, a head secured to the shaft, a stationary friction device against which. the

headrotates, a pawl lifter, and manually operated means for simultaneously releasing thefriction device and for actuating the pawl lifter whereby the shaft may be turned byhand.

4. A loom having, in combination, a warp beam, a let-off mechanism including'a pawl and ratchet, a shaft on which the ratchet is mounted extending to and terminating at the frontof the loom, a head secured to the front end of the shaft, a sliding friction dog, means for normally pressing the friction dog, into engagement with the head, a pawl lifter, a manually operated cam on the, head for sliding the dog out of engagement therewith,

and a connectionlbetween the dog and the pawl lifter for simultaneously operating the latter to permit rotation of the shaft by hand.

- 5. A loom having, in combination, a. Warp beam, a let-off mechanlsm includ ng a pawl and ratchet, a shaft on which the ratchet is mounted extending tothe front of the gloom,

gearing for rotating the. warp beam from the'shaft, a head secured to thefront of the shaft, sliding friction dog normally engag- V ing the head, a manually operated. camon -the v head adapted to move the dog out of engage ment therewith, a lever ass'ociatedwith the dog, and a pawl lifter connected with the lever whereby a manual operation of the cam releases the friction dog from the head and actuates the pawl lifter to disengage the pawl from the ratchet andjpermit rotation of the shaft by hand from the front ofthe loom.

6. A loom having, in combination, :a warp beam, a let olfmechanism, a roll over whlch the warps pa'ss,means for mounting the roll to permit movement thereof .in accordance with the warp tension, means controlled by the movement of the roll to vary the let off, a spring to resist movement of theroll, the V spring being connectedwith the roll mount- 7 ing and extending to the bottom of the loom, a warp follower, means for pivoting the fol lower at the bottom of theleom, and a m0v' able abutment for the lower end of the spring adapted to be adjusted in'position by the foilower tovary thesensitivity of the let off control in accordance with theisizeof the warp beam.

Jo AsNonT-nnon Intestimony. whereof I'hav signed name to this specification. 

